The Black family is really, really complicated, and I feel like you did a great job of portraying that, especially at the beginning before Sirius left the house. Regulus definitely felt a bit torn to me, which I liked, because that's how I imagine he would feel; on one hand, Sirius is his brother, and it's only natural that he care about him. On the other, he's much more sympathetic to his family's way of looking at things, which means he's kind of caught between a rock and a hard place. I'd never thought about it before, but in a lot of ways, Regulus's life probably got easier after Sirius left.

I really liked the Muggles he encounters, too. They add a human element to your story that manages to stay just on this side of realistic (particularly the woman in the diner - the man was stretching it a bit, but I can suspend my disbelief), and adds a nice contrast to Sirius's family as we saw them at the beginning of the story. A stranger feeds him for free, but his mother burns him off the family tree. A stranger helps him and gives him a bike (sort of), and his mother locks him out of his Gringotts vault. It really says all you need to know about the Blacks.

My only issue was that I did feel like you could have been a bit more imaginative. This is a good story that's well-written, and you certainly fulfilled the prompt nicely, but it didn't pop - I didn't feel like you really used your creativity and delved deeper into the story, if that makes sense. I'm not saying it wasn't good or enjoyable, because it absolutely was - just that I would have liked to see a little something extra, if that makes sense.